Working backward to solve problems - Maurice Ashley

Transcriber: Andrea McDonough Reviewer: Bedirhan Cinar

翻译人员: Qiyun Xing 校对人员: Jiawei Ni

There's a myth that grandmasters can see ten,

有这样一种传说：

fifteen, twenty moves ahead.

认为国际象棋大师能够预知后面的十步、十五部、甚至二十步

And it's a great myth because I'm a grandmaster

而这也仅是个传说，因为我是个象棋大师

and it makes me look like a super freaking genius.

所以大家觉得我是个超级聪明的天才

But the truth is,

事实上

in just the first four moves,

在一开始的四步之内

there are 318 billion ways you could play.

就可以演变出3180亿种不同的方式

Now, that would be cool if I could pull that off,

所以如果我真的有这个能力就实在太酷了

but grandmasters just can't, it's too much.

但大师们其实并没有这个能力，因为可能性实在太多了

So we use different techniques to be able to look ahead.

所以我们用其它的技巧来进行预判

And some of these techniques include chunking,

有些技巧包括‘知识组块’

which means taking a group, a chess position,

意思是只看盘面中的一部分棋子

and seeing what possibilities can come from just that group;

预测其可能性

or pattern recognition,

还有‘类型识别’

which is just going over a lot of positions that look very similarly

从许多相似的盘面中

and extrapolating truths from that;

识别出最接近的一种

the stepping-stone method,

或是用‘跳板法’

which is to take a position, freeze it in your mind,

把当下的盘面刻在脑海

and go from there to guess the next position.

来推测下一步

But one of my favorites

但是我最喜欢的

that I love to solve these kind of chess puzzles,

打破迷局的方法是

is called retrograde analysis.

‘回溯分析’

And what you do with retrograde analysis

这个要怎么做呢

is that in order to look ahead, it pays to look backwards.

就是通过往回倒着分析来预测下一步

Now, why is this so useful?

那么这招为什么管用呢

Well, in chess, it's a very complicated case.

在国际象棋里这很复杂

You got all these chess pieces, it's 32 pieces,

你有32个棋子

but after five moves, the position starts to evolve a little bit.

五步之后，局面慢慢发展

And the game starts to go on

游戏真正开始

and you see the chess position get a little simpler,

象棋盘面逐渐清晰明了

and a little bit simpler, and less pieces on the board,

棋子越少盘面越简单

until finally --

最终

in this case, a game that I played in a tournament in Foxwoods,

在我在Foxwoods参加的比赛中

it gets to something like this.

最终盘面变成了这样

When great players play, it often gets to something like this.

当出色的棋手下棋时，盘面常与之类似

You don't see some easy, early checkmate.

不太可能轻松将死对手

Grandmasters see through all that stuff.

国际象棋大师会看破这一切

What you see is some end game, something really, really simple.

有些棋局，盘面简单

And we like to study things like this,

我们喜欢研究这样的棋局

grandmasters do,

大师们也爱研究

so that if we get to them, we know how to play them cold,

以便以后遇到时便可冷静应对

but also so that we can steer the position that's in front of us,

我们也可以引导棋局成为这种局面

the more complex ones you saw earlier,

之前看到的复杂形势

to something this easy,

就会变的容易

something this simple.

很简单

So in this way, when you're dead,

你将以这种方式被将死

I already knew like ten moves ago,

而我十步前就知道了

because I knew where we were going.

因为我知道接下来盘面会如何变化

Now, why is this so effective?

为什么这这么有效呢？

Well, it's something about the human mind, the problem with the human mind.

是因为人类的思考

We're very logical creatures.

人类非常的有逻辑

So I want you to play along with me a few games.

我希望你们和我玩几个小游戏

Take a look at this sentence.

读一下这句话

[After reading this sentence,

读完这句话后

you will realize that the brain doesn't recognize a second "the."]

你并没意思到有两个the

Now, most of you reading the sentence the second time around

直到你读第二遍

will realize that you missed the word "the"

你才发现漏第一次读的时候

the first time around.

漏掉了一个the

Your mind is very logical, it proceeds forward,

你的大脑非常的有逻辑，当它运转时

it just ignores anything that breaks with its logical stream,

它自动忽略不符合逻辑的事

and so you don't see the word "the" the first time,

所以你第一次并没发现

the second "the," the first time you read it.

第二个the

But if you read this sentence backwards, you would automatically catch it.

但是如果你倒着读这句话，你就会发现

You'd go backwards, and you get to "brain," you get to "the,"

你读到brain，然后读到the

and then you say, "Whoa, there are two 'the's' in the sentence."

你会发现这句话有两个the

This is a really cool trick for proofreading papers.

这个倒读的技巧对校正论文很有帮助

You're writing your paper and there are these silly mistakes.

你的文章里有一些愚蠢的错误

Why are these mistakes in my paper?

为什么会有这些错误呢？

You read it backwards, you'll catch all of them.

你倒着读文章就会发现错误

Alright, let's go on to this problem, an interesting problem.

让我们再看一个有趣的问题

"Bacteria that double every 24 hours

细菌每24小时分裂一次

fill a lake it has infested after precisely 60 days.

60天可覆盖一个被细菌感染的湖

On what day was the lake half-full?"

那么什么时候半个湖面被细菌覆盖呢？

Now, a lot of people see this problem

许多人看到这个问题

and they'd think, "30, like, you know, you split it in half."

他们觉得是30天，你知道的，刚好一半的时间

Well, that's not the right answer.

但是这不是正确的答案

And also people might want a calculator.

许多人也会想用计算器算

It's too big, it's math, it's boring, I don't want to do that either.

无聊的数学，数太大。我也不想算。

But if you do this problem backwards, you get the answer right away.

但是如果你反向计算，你立刻就得到答案

What's the answer? 59, obviously.

答案是59，很明显

You start at the end, you go backwards,

你从最后一天开始，往回推

it's like, "Oh yeah, it's half-full, the answer is 59."

半满就是前一天，第59天

Here's another puzzle, a little bit more complicated.

还有另一个题，稍稍有点复杂。

You have six numbers, 1 through 6.

有1-6 六个数字

The cards are face down.

卡片面朝下

You and I are going to pick a card.

你和我一人抽一张牌

You pick a card and you look at it and it says the number 2.

你抽了一张牌看一下，是2

I look at my card, I think about it for a minute

我看着我的牌，想了下

and I say, "I want to trade."

然后我说‘我想和你交换’

The reason I want to trade,

我想换的原因是

we're going to trade to see who has the highest number at the end.

我们要比一比最后谁拿的牌大

Do you trade with me?

你想和我交换么？

Most people say, "Of course, I got a 2, 2 sucks!

很多人说：当然了，我只抽到2，2太小了

There are four numbers higher, probability says I'm going to do better."

有四个牌都比这个大，按概率将我也会换到更好的牌的

Wrong answer, you're playing a grandmaster.

错了。你可是在和一个国际象棋大师玩

You start from the back and you work it out.

反向思考看看，你就会明白

If I had the number 6, would I offer to trade?

如果我有6，我会想换么？

Of course not, I'm not dumb.

当然不会，我又不傻

What about the number 5?

如果我拿的是5呢？

Probably not either, because you're not going to say yes if you have a 6.

很可能也不会，如果你有6你是不会愿意换的

If 5 is not going to trade and 6 is not going to trade,

如果5和6都不会换

4 is going to be like,

4的情况就是

"I'm not trading either, because 5's and 6's don't trade."

我也不会换，5和6都不换给我

So you see what happens as we work backwards.

所以这就是反向思考的结果

3 is going to realize: 4, 5, and 6 -- they don't trade,

3和4、5、6一样不会换给我

so the offer is definitely a 1

所以提议要换的人拿的是1

and all of you who said yes, thanks for your money.

刚才愿意换牌的人，谢谢你们的赌金

(Laughter)

（笑）

So, this retrograde analysis is used in different places.

所以回溯分析可以用在不同的领域

It's used to prove intoxications hours after an alleged DUI

宾州警方用这个方法证明

by Pennsylvania police officers,

酒驾案的司机真的有喝酒

which is kind of cool.

这非常厉害

Well, it means don't drink and drive.

这告诉我们不要酒驾

The use of retro-analysis is used in law, science, medicine, insurance,

回溯分析也被用在法律、科学、医药、保险

stock market, politics, career planning.

股市、政治、职业规划中

But I find its use to be in a more interesting place,

但是我发现它可以用在一个更有意思的地方

maybe one of the most interesting uses is in this movie,

最有意思的应用可能是在电影里

which I know a lot of you know,

我想你们很多人都知道

"The Curious Case of Benjamin Button,"

‘本杰明巴顿奇事’

where Brad Pitt plays a guy who's living his life backwards.

布拉德皮特扮演一个人生倒着过的角色

And what this movie makes me think of is that great quote,

这个电影让我想到一句伟大的格言

that quote you often hear from people who are older,

你们经常从长辈那里听到

that youth is wasted on the young.

青春被年轻人浪费

Well, if you can see the end game,

如果你可以预见人生结局

your youth will not be wasted on you.

你就不会荒废青春了

Thank you very much.

非常感谢

(Applause)

（鼓掌）